A technique has been proposed that, in an environment where a plurality of storage apparatuses are operated, virtualizes the storage apparatuses into one virtual storage apparatus to thereby facilitate the operation and management. According to this technique, a host can access a virtual logical volume (hereinafter referred to as a “virtual volume”) provided by the virtual storage apparatus, from any of physical storage apparatuses comprising the virtual storage apparatus. Data of one virtual volume is stored in a manner distributed among the storage apparatuses sharing the virtual volume. Accordingly, in the case where a plurality of hosts use an identical virtual volume, access can be distributed so as not to concentrate loads on a controller of one storage apparatus. Even in the case of depleting the free space of one storage apparatus, a free space of another storage apparatus can be used. It is thus advantageous to negate the need to individually manage free spaces for respective storage apparatuses.
For instance, in the virtual storage apparatus, a pool in which the storage areas of respective storage apparatuses are integrated is comprised. A virtual volume based on a thin provisioning technique is created on the pool. The created virtual volume is provided for the host. The host can access data in the virtual volume from any of storage apparatuses sharing the virtual volume. In the case where the storage apparatus receives a read request issued by the host, this storage apparatus identifies which storage apparatus stores the data to be read, acquires the data to be read from the identified storage apparatus and then returns the data to the host. The storage apparatus receives a write request issued by the host, and selects a destination region for the new data from among free regions in all the storage apparatuses sharing the pool if the request is a write request for new data.
Patent Literature 1 discloses a technique of managing paths for a storage apparatus.